from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A small valve or faucet used to drain or reduce pressure, as from a boiler.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A small valve, spout, or faucet operated by hand, usually used to release pressure or drain fluid.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. regulator consisting of a small cock or faucet or valve for letting out air or releasing compression or draining
Perhaps pet1 + cock1.(American Heritage® Dictionary of the English Language, Fourth Edition)